This invention relates to a foreign object separator including a multi zone detection system, and means for providing a fluid blast controlled by said detection system to remove foreign objects from a single flowing stream of material. In a known apparatus one of a series of fluid valves allocated to a number of detection zones may be operated on detection of a foreign particle. By appropriate timing the valve is actuated at the moment the particle arrives opposite an air blast nozzle connected to the valve.
A problem arises where an object which may be as large as a tag or label, extends beyond a single detection zone since due to the fall-off of air velocity at the zone edges the blast may be insufficient to remove the object. It is known that zone overlap can be provided by mechanical means, but with this fixed overlap a system cannot be easily optimised.